Neurochemical organization of inferior pulvinar complex in squirrel monkeys and macaques revealed by acetylcholinesterase histochemistry, calbindin and Cat‐301 immunostaining, and Wisteria floribunda agglutinin binding

To investigate whether the inferior pulvinar complex has a common organization in different primates, the chemoarchitecture of the visual thalamus was re-examined in squirrel monkeys (Saimiri sciureus) and macaques (Macaca mulatta). The inferior pulvinar (PI) complex consisted of multiple subdivisions and encompassed the classic PI, and adjacent ventral parts of the lateral and medial pulvinar (PL and PM, respectively). In keeping with nomenclature suggested previously for macaques, the PI subdivisions were termed the posterior, medial, central, lateral, and lateral-shell (PIP, PIM, PIC, PIL, and PIL-S). In both species, PIP was intense for calbindin, light for acetylcholinesterase (AChE), and very light for Wisteria floribunda agglutinin (WFA) histochemistry. The PIM was calbindin poor, AChE rich, and moderate for WFA. The PIC was calbindin intense, lighter for AChE, and exhibited little WFA binding. PIL and PIL-S contained populations of large calbindin or WFA cells that were more numerous in PIL-S. Although staining with the monoclonal antibody Cat-301 differed between macaques and squirrel monkeys, the same subdivisions were displayed. Moderately dense, patchy Cat-301 stain was found in PIM of macaques, whereas in squirrel monkeys PIM was light. Connections of the rostral dorsolateral (DLr) and middle temporal (MT) areas of visual cortex in squirrel monkeys were compared with PI subdivisions revealed by the newer histochemical methods in the same cases. The major connections of DLr were with PIC and of MT were with PIM. J. Comp. Neurol. 409:452–468, 1999. © 1999 Wiley-Liss, Inc.